1. Field of the Invention
The present invention relates generally to a method of manufacturing an article of fiber-reinforced composite material. More particularly, the invention relates to a method of manufacturing an article of fiber-reinforced composite material having at least one locally placed, sharply curved portion, such as a recess, a groove, a protrusion, a ridge or the like.
The invention also relates to a specific tool component for forming in an article of fiber-reinforced composite material at least one locally placed, sharply curved portion.
2. Description of Related Art
When producing strong light-weight products of a fiber-reinforced composite material for e.g. the aircraft industry, such as control surfaces, flaps, doors, hatches, integral panels or the like, problems may arise to accurately form sharply curved recesses or protrusions in the product due to the limited ability of a flexible vacuum membrane to follow the profile of such sharply curved sections of the matrix and, hence, to properly depress the lay-up of a fiber sheet laminate into these sections during the evacuation of the membrane. This will necessitate the addition step of applying external forces to the membrane by means of an autoclave or the like. It is known to use auxiliary tool components to improve the forming of corner sections of products of fiber-reinforced composite material. US 2006/0068170 A1 discloses a method and a tooling aid for applying pressure on a fiber sheet laminate in order to properly form two opposite corner portions of an entirely U-shaped product. For this purpose a flexible U-shaped auxiliary tool element having a concavely curved web or base section and two opposite corner sections is positioned over the laminate in a female mold. When an enclosing sealed membrane is evacuated, the latter exerts a pressure on the flexible, curved base section of the tool element, thereby causing the base section to flex downwardly to stretch the underlying laminate while at the same time expanding the corner portions of the tool element outwardly towards the corresponding corner parts of the mold surface. However, such a tool element is not suitable for forming products of fiber-reinforced composite material having at least one locally placed, sharply curved portion, such as a recess forming a narrow groove or a protrusion forming a ridge of the product, i.e. where the membrane is not capable of depressing the laminate close enough to the mold surface.
Moreover, EP 0 992 336 A1 discloses use of one or more auxiliary stiff support elements for resin-impregnating and hardening of a preformed composite article, e.g. an L-shaped product, in a further process step following a pre-forming step, where the evacuation of flexible bags is not sufficient to support the composite material. Such support elements are not suitable as auxiliary tools for forming in one single thermoforming step and without using external forces of e.g. an autoclave locally placed, sharply curved portions in a lay-up of fiber sheets by using an enclosing evacuateable membrane.